The global ocean circulation system transports heat worldwide and affects climate in many areas. For example, Europe would have much colder winters if it were not for the Gulf Stream. Winds blow surface waters and cause ocean currents. But the waters below the depths of the wind's influence flow...

Density is a measure of the mass per unit volume of a substance. The density of seawater depends on many factors such as the concentration of salt dissolved in it and its temperature. This demonstration shows different gradients of density in ocean water.